Influence of a flexible tail on the performance of a foil hovering near the ground: Numerical investigation

The influence of a flexible tail on the performance of a foil hovering near the ground is numerically investigated in this study. A NACA0015 foil arranged in close proximity to the ground is imposed with a synchronous harmonic translation and rotation. A flat plate attached to the trailing edge of the foil is adapted to model a tail. The tail is either rigid or passively deformable. To conduct numerical simulations, a robust immersed boundary-lattice Boltzmann method is employed. At a Reynolds number of 100 and the position of the rotating axis at third chord, the influences of the mass and flexibility of the tail as well as the distance between the rotating axis and the ground on the aerodynamic performance are systematically examined. Based on the results established, it is found that for the case of a flexible tail both the drag reduction and lift enhancement are observed compared to the case of a rigid tail. In addition, high ratios between the lift and the drag as well as between the lift and the power input are found when the mass and flexibility of the tail are low.